The present invention relates to a device for connecting a high-pressure line to an accumulator tank according to the preamble of claim 1.
One way of reducing discharges of emissions from diesel engines is to inject the fuel at very high pressure. A so-called “Common Rail” system is commonly used for effecting injection at a high pressure in the combustion spaces of a diesel engine. A Common Rail system comprises a high-pressure pump which pumps fuel at a very high pressure to an accumulator tank (“Common Rail”). The pressure in the accumulator tank during operation may be 350 bar or higher. The fuel in the accumulator tank is intended to be distributed to all the cylinders of the combustion engine. Fuel from the accumulator tank is injected into the combustion spaces of the respective cylinders by electronically controlled injection means. The fact that the pressure in the accumulator tank and in the high-pressure line which leads the fuel from the high-pressure fuel pump to the accumulator tank is so high imposes severe requirements upon the connection of the high-pressure line to the accumulator tank if it is to remain tight.
A known practice is to provide accumulator tanks with a permanent nozzle to make it possible to connect a high-pressure line, but providing an accumulator tank with a permanent nozzle involves a relatively large amount of work and is therefore expensive, since it has to be welded, forged or soldered firmly to the accumulator tank.
U.S. Pat. No. 6,408,826 refers to a device for connecting a high-pressure line to a cylindrical accumulator tank. The device comprises a connecting means which has a cylindrical hole so that it can be fastened to the accumulator tank. The connecting means also comprises a tubular threaded portion intended to cooperate with a nut in order to fasten an end of the high-pressure line to the accumulator tank. A problem with such a connection arises in cases where the cylindrical hole in the connecting means does not quite match the shape of the outside surface of the accumulator tank. This may result in the accumulator tank acquiring an undesirable oblique position relative to the tubular portion of the connecting means, resulting in the contact surfaces of the high-pressure line and of the accumulator tank assuming a corresponding oblique position when they are brought together. This may lead to play between said contact surfaces in an assembled state, with consequent leakage.